Questions 11
- What are the consequences of omitting a significant variable in the model?
- In what special case we can obtain valid estimates of parameters even so significant variables were omitted from the model?
- Why the variables which are not significant should be deleted from the model?
- Parameters related to variables {$x_1$} and {$x_2$} are positive. The variables are negatively correlated. What will be the effect of omitting variable {$x_1$} in the regression on the estimate of the parameter related to variable {$x_2$}?'
- Explain when we are saying that the observation is unusual and when we can identify an observation as erroneous.
- In what case an unusual observation has a large impact on regression results?
- What statistics are use to detect unusual and erroneous observations?
- In what case we are talking about perfect collinearity? How we are solving this problem?
- What are the consequances of imperfect collinearity? What statistics is used to detect the presence of severe collinearity in the model?